The author of the blockbuster “Harry Potter” series is back to writing and this time she’s writing for adults. Rowling has signed an agreement with publisher Little, Brown in the US and Britain to publish her first novel for adults, the publisher announced Thursday. Little, Brown has been tightlipped about the details, refusing to release the title, release details, or genre of the forthcoming book.

In choosing to publish her first adult novel with Little, Brown, Rowling has deliberately decided not to go with Bloomsbury, which published the Harry Potter series in Britain, or Scholastic, which published it in the US.

“Although I've enjoyed writing it every bit as much, my next book will be very different to the Harry Potter series, which has been published so brilliantly by Bloomsbury and my other publishers around the world,” Rowling said in a statement released by Little, Brown. “The freedom to explore new territory is a gift that Harry's success has brought me, and with that new territory it seemed a logical progression to have a new publisher. I am delighted to have a second publishing home in Little, Brown, and a publishing team that will be a great partner in this new phase of my writing life.”

The good news – while Potterphiles await Pottermore and the Harry Potter ebooks, Little, Brown promises that it will publish Rowling’s adult novel “both in print and e-books” simultaneously.

Of course, Rowling’s forthcoming novel is almost guaranteed to be a bestseller – her Harry Potter books have sold more than 400 million copies around the world, been translated into 70 different languages, and made the author a self-made billionaire adored by her fans.

Nonetheless, it’ll be tough for Rowling to attract the same mass following as her Harry Potter series did. Like child actors, children’s authors sometimes struggle to transition to adult novels. Writes the AP, “Winnie the Pooh creator A.A. Milne, a successful playwright in his early years, once confessed that he was forced to say "goodbye to all that" after his beloved books about the bear and friends. Margaret Wise Brown, author of the classic "Goodnight Moon," tried for years to write stories for The New Yorker.”

Still, Rowling has rocked the publishing world before, by making children’s books popular again, and by showing publishers that children’s books weren’t just for kids. It’s a new era in publishing, one in which books like Stephanie Meyer’s “Twilight” novels and Suzanne Collins’ “Hunger Games” trilogy are as popular with kids as they are with parents. Rowling could draw a similar mixed audience.

One thing is clear: expectations for the new Rowling novel are immense. Tweets Rowling fan Natalie Summers: “JK Rowling announcing a new book is almost like god announcing a follow-up to the Bible.”